Numerous studies have been performed to determine the phase behavior of surfactant-oil-water systems. Results from these studies have shown that mixtures of water and oil separate within a well-defined temperature interval into three liquid phases (an aqueous phase, an oil phase, and a surfactant rich phase) with the maximum mutual solubility between water and oil and the lowest inter-facial tension being found in the surfactant rich phase. Numerous attempts to improve oil solubilization in these systems have been tried, such as using a surfactant with both a larger hydrophilic group and larger hydrocarbon tail, and the use of an additive lipophilic linker. More recently, Salager et al. (Proceeding of the CESIO 4th World Surfactant Congress, Barcelona, Vol. 1, 223-234 (1996)) has shown oil solubilization may be improved in these ternary systems through the use of an extended chain surfactant.
In household and industrial-institutional cleaning products, the surfactants used are generally composed of a lipophilic group attached to a hydrophilic group. In aqueous solution, the surfactant molecules associate to form micelles which can solubilize soils or stains present on an article. Where cleaning product clarity and homogeneity are important considerations, the surfactant is incorporated into an oil-in-water microemulsion. These cleaning products contain a variety of different sufactant systems in 5-20% solubilized oil which are then diluted with water prior to use. The surfactant systems generally employed in these cleaning products include a mixture of anionic or non-ionic surfactants and a short chain alcohol to help solubilize the oil phase and prevent liquid crystal formation. While short chain alcohols are effective, they contribute to the volatile organic solvent content (VOC) of the product and pose flammability problems. Thus, it would be desirable to produce a VOC-free surfactant system, capable of forming a single phase microemulsion with a variety of different oils, which can be incorporated into cleaning products to enhance cleaning performance.